Imaging apparatus

ABSTRACT

After a first cam bear has unlocked a blade lever, a second cam gear is driven from a mirror-down position to a mirror-up position. Accordingly, a first blade and a second blade are driven in a direction of opening an aperture by an urging force of a blade return spring before a mirror starts a mirror-up operation.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an imaging apparatus.

2. Description of the Related Art

Japanese Patent Application Laid-Open No. 2008-180815 discusses animaging apparatus that uses a focal plane shutter and an electronicshutter in combination with each other to execute an imaging operation.The conventional imaging apparatus starts an exposure operation by usingan electronic shutter function of an image sensor. In addition, theconventional imaging apparatus controls a blade group constituted by amechanical shutter to end an exposure operation.

In the above-described conventional imaging apparatus, after locking adrive lever by energizing an electromagnet, a set lever starts driving amirror in a mirror-up direction. After the mirror-up operation, a bladelever is unlocked and an aperture formed by a blade group is opened.Subsequently, when the energization of the electromagnet is discontinuedat a predetermined timing, the drive lever and the blade lever aredriven simultaneously in a direction of closing the aperture.

However, in the imaging apparatus discussed in Japanese PatentApplication Laid-Open No. 2008-180815, the blade group hops when theblade lever is unlocked and the aperture by the blade group is opened.Similarly, during a mirror-up operation, the mirror hops.

In general, the urging force (spring force) of a blade return springwhich energizes a blade lever in a direction of opening an aperture by ablade group is smaller than the spring force of a spring that drives amirror in the mirror-up operation. Accordingly, it takes a long time incancelling the hop. However, in the imaging apparatus discussed inJapanese Patent Application Laid-Open No. 2008-180815, the blade leveris unlocked and the aperture by the blade group is opened after themirror-up operation is started.

Accordingly, the exposure operation by the electronic shutter functioncannot be started until the hop of the blade group ends even after thehop of the mirror has ended. Therefore, a time period from a timing ofdisappearance of a viewfinder image to a timing of start of exposure maybecome long.

SUMMARY OF THE INVENTION

According to an aspect of the present invention, an imaging apparatusincludes a mirror configured to advance or retract into or from aphotographic optical path, a shutter blade configured to close and openan aperture, a blade lever connected with the shutter blade, a bladereturn spring configured to urge the blade lever in a direction in whichthe aperture is opened by the shutter blade, a drive lever configured topress the blade lever in a direction in which the aperture is closed bythe shutter blade, a blade drive spring configured to urge the drivelever in a direction in which the aperture is closed by the shutterblade, a first member configured to lock a position of the blade leverto cause the shutter blade to shift to a state of closing the aperture,and a second member configured to cause the mirror to advance into thephotographic optical path at a first position and to cause the mirror toretract from the photographic optical path at a second position. In theimaging apparatus, the second member is driven from the first positionto the second position after the first member has unlocked the bladelever so that the shutter blade is driven in the direction of openingthe aperture by an urging force of the blade return spring before themirror starts an operation for retracting from the photographic opticalpath.

According to an exemplary embodiment of the present invention, a timeperiod from a timing of a disappearance of a viewfinder image to atiming of start of exposure can be reduced.

Further features and aspects of the present invention will becomeapparent from the following detailed description of exemplaryembodiments with reference to the attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate exemplary embodiments, features,and aspects of the invention and, together with the description, serveto explain the principles of the present invention.

FIGS. 1A and 1B are exploded perspective views of a shutter unit.

FIGS. 2A through 2D illustrate a drive lever, a blade lever, and aratchet.

FIG. 3 illustrates a state in which a blade drive spring and the ratchetare assembled to the drive lever.

FIGS. 4A through 4C illustrate the ratchet.

FIGS. 5A and 5B illustrate a first cam gear and a second cam gear.

FIG. 6 is a timing chart illustrating operation timings of a mirrorlever, a main mirror, the blade lever, the drive lever, a coil, a bladegroup, and an image sensor.

FIGS. 7A through 7C illustrate a state in which the shutter unit is in apre-release standby state.

FIGS. 8A through 8C illustrate a state in which the shutter unit is in ablade lever unlocked state.

FIGS. 9A and 9B illustrate a state in which the shutter unit is in amirror-up live view state.

FIGS. 10A through 10D illustrate a state in which the shutter unit is inan unset state.

FIGS. 11A and 11B illustrate a state in which the shutter unit is in ablade travelling state.

FIGS. 12A and 12B illustrate a state in which the shutter unit is in ablade travel complete state.

FIGS. 13A and 13B illustrate a state in which the shutter unit is in amirror lever charge complete state.

FIGS. 14A and 14B illustrate a state in which the shutter unit is in ablade lever lock enabled state.

FIGS. 15A and 15B illustrate a state in which the shutter unit is in adrive lever charging state.

FIGS. 16A and 16B illustrate an exemplary shape of a blade cushioningmember and a blade contact member.

FIGS. 17A through 17D illustrate a method for assembling the bladecushioning member to a shaft portion.

FIGS. 18A through 18C are perspective views illustrating a state inwhich a first blade contact member and a second blade contact member areassembled to the blade cushioning member.

FIGS. 19A through 19H illustrate an exemplary method for assembling theblade cushioning member to the shaft member.

FIG. 20 is a central-plane cross section of a digital single-lens reflexcamera body, which is an imaging apparatus according to an exemplaryembodiment of the present invention, and an interchangeable lens.

DESCRIPTION OF THE EMBODIMENTS

Various exemplary embodiments, features, and aspects of the inventionwill be described in detail below with reference to the drawings.

Now, a shutter device, which implements the present invention, and animaging apparatus equipped with the shutter device, will be described indetail below with reference to FIGS. 1A, 1B, and 20.

FIG. 20 is a central-plane cross section of a digital single-lens reflexcamera body 101, which is an imaging apparatus according to an exemplaryembodiment of the present invention, and an interchangeable lens 201.

The interchangeable lens 201, which can be detachably attached to thecamera body 101, is fixed by a camera mounting portion 102 and a lensmounting portion 202. When the interchangeable lens 201 is mounted, thecontact portion 103 of the camera body 101 and the contact portion 203of the interchangeable lens 201 are electrically connected with eachother. At this timing, the camera body 101 detects that theinterchangeable lens 201 has been mounted. In addition, the camera body101 supplies power to the interchangeable lens 201 via the contactportions 103 and 203 and communicates with the interchangeable lens 201to control the interchangeable lens 201.

A light flux that has travelled through a focus lens 204 of theinterchangeable lens 201 is incident to a main mirror 6 of the cameramain body 101. The main mirror 6 can advance and retract into and from aphotographic optical path. The main mirror 6 is a half mirror. The lightflux reflected on the main mirror 6 is guided to a viewfinder. Inaddition, the light flux that has reflected from the main mirror 6 isfurther reflected downwards by a sub mirror 105 to be guided to a focusdetection unit 106.

The focus detection unit 106 detects an amount of defocus in the focuslens 204. In addition, the focus detection unit 106 calculates a lensdrive amount for moving the focus lens 204 to achieve an in-focus stateof the focus lens 204. When the calculated lens drive amount istransmitted to the interchangeable lens 201 via the contact portions 103and 203, the interchangeable lens 201 controls a motor (not illustrated)to move the focus lens 204 and executes focusing.

The main mirror 6 is supported by a main mirror supporting frame 107.More specifically, the main mirror 6 is pivotably supported by arotation shaft portion 6 b. In addition, the sub mirror 105 is supportedby a sub mirror supporting frame 109. The sub mirror supporting frame109 is pivotably supported by a hinge shaft (not illustrated) and canpivot around the main mirror supporting frame 107.

The light flux guided to the viewfinder forms an object image on afocusing screen 110. A user can observe the object image on the focusingscreen 110 via a pentagonal prism 111 and an eyepiece lens 112.

A shutter unit 100 is provided behind the sub mirror 105. In an initialstate, a blade group is closed. An optical low-pass filter 114 isprovided behind the shutter unit 100.

An image sensor 116 and a cover member 117 are provided behind theoptical low-pass filter 114. The image sensor 116 is supported by animage sensor holder 115, which is fixed to a housing by a screw (notillustrated). The cover member 117 protects the image sensor 116.

A rubber member 118 supports the optical low-pass filter 114 andfunctions as a close seal between the optical low-pass filter 114 andthe image sensor 116. During shooting, alight flux that has passedthrough the optical low-pass filter 114 is incident to the image sensor116.

FIG. 1A is an exploded perspective view of the shutter unit 100 viewedfrom the front. FIG. 1B is an exploded perspective view of the shutterunit 100 viewed from the back side thereof. Referring to FIG. 1A, anaperture 1 a is formed in the center of a shutter base plate 1. Shafts 1b through 1 d are formed on the shutter base plate 1.

A drive lever 11, a blade lever 15, and a ratchet 16 are pivotablysupported by the shaft 1 b. A first cam gear 21 is rotatably supportedby the shaft 1 c. A second cam gear 22 is rotatably supported by theshaft 1 d. The first cam gear 21 functions as a first member. The secondcam gear 22 functions as a second member.

The drive lever 11 and the ratchet 16 are pivotably supported around theshaft 1 b. The first cam gear 21 is pivotably supported around the shaft1 c. The second cam gear 22 is pivotably supported around the shaft 1 d.An auxiliary base plate 31 is fixed onto the shutter base plate 1.

The blade lever 15, which is pivotably supported by the drive lever 11,pivots around the shaft 1 b similar to the drive lever 11. Shaft bearingholes, into which the shafts 1 b through 1 d are inserted, are given tothe auxiliary base plate 31. The drive lever 11, the blade lever 15, theratchet 16, the first cam gear 21, and the second cam gear 22 aresandwiched between the shutter base plate 1 and the auxiliary base plate31.

A shaft 31 a is formed on the auxiliary base plate 31. A mirror lever 36is freely and pivotably supported around the shaft 31 a. A mirror leverdrive spring 39 is latched on the mirror lever 36. The mirror leverdrive spring 39 is urged in a clockwise direction in FIG. 1 (i.e., in adirection of ascending the main mirror 6). The main mirror 6oscillatingly pivots around the rotation shaft portion 6 b.

With the above-described configuration, the main mirror 6 can be movedbetween a mirror-down position and a mirror-up position. The mirror-downposition is a position at which the main mirror 6 remains stationary atan angle of 45° against a photographic optical axis to guide an imaginglight flux towards the pentagonal prism 111. On the other hand, themirror-up position is a position at which the main mirror 6 is keptstationary at a position to which the main mirror 6 is retracted fromthe imaging light flux to guide the light flux towards the image sensor116.

A main mirror drive spring 7 is latched onto a shaft portion 6 a of themain mirror 6. The main mirror drive spring 7 presses the main mirror 6in a mirror-down direction. Ratchet teeth 16 a are formed on the ratchet16. An engaging claw portion 31 b, which is an engaging member forengaging with the ratchet tooth 16 a, is provided to the auxiliary baseplate 31. A photosensor 32, which detects a pivoting position of theblade lever 15, is mounted on the auxiliary base plate 31.

Referring to FIG. 1B, a yoke 33 and a coil 34 are fixed by the screw 35to the auxiliary base plate 31. By applying a voltage to the coil 34, amagnetic force is generated on the yoke 33. As illustrated in FIG. 1A, afirst fixing portion 38 a and a second fixing portion 38 b are formed ona flexible printed circuit (FPC) 38. The auxiliary base plate 31 isfixed to the flexible printed circuit 38 at the first fixing portion 38a. The shutter base plate 1 is fixed to the flexible printed circuit 38at the second fixing portion 38 b.

The flexible printed circuit 38 is connected with the coil 34 and thephotosensor 32 via the first fixing portion 38 a. A phase patternportion 38 c is formed on the second fixing portion 38 b of the flexibleprinted circuit 38. The phase pattern portion 38 c detects the phase ofa phase armature 23, which is mounted to the first cam gear 21.

A semicircular cushioning member 3 is fixed on top of an arc-shapedperforation le, which is formed on the shutter base plate 1. Thesemicircular cushioning member 3 is made of an elastic material, such asrubber.

As illustrated in FIG. 1B, a cover plate 2 is fixed on a back surface ofthe shutter base plate 1. An aperture 2 a is formed in the center of thecover plate 2 at a position substantially identical with the position ofthe aperture 1 a of the shutter base plate 1. The apertures 1 a and 2 arestrict a light flux going through the shutter unit 100.

A blade chamber, in which the blade group is provided, is formed betweenthe shutter base plate 1 and the cover plate 2. The blade group isconstituted by a first blade 41, a second blade 42, a main arm 43, and asub arm 44.

The first blade 41 and the second blade 42, which are shutter blades,are made of polyethylene terephthalate (PET) that contains a blackening.The first blade 41 and the second blade 42 are pivotably supported bythe main arm 43 and the sub arm 44 by using a pin 45.

The main arm 43 is pivotably supported around a shaft 1 f, which isprovided on the shutter base plate 1. The sub arm 44 is pivotablysupported around a shaft 1 g, which is provided on the shutter baseplate 1.

The main arm 43 turns around the shaft 1 f. The sub arm 44 turns aroundthe shaft 1 g. Accordingly, the first blade 41 and the second blade 42execute a parallel link action. A hole 43 a, which is a hole forengaging the main arm 43 with an engaging portion 15 a of the bladelever 15, which will be described below, is formed on the main arm 43.

The blade lever 15 functions as a blade lever connected with the firstblade 41 and the second blade 42. A blade return spring 46 is latched onthe sub arm 44. The blade return spring 46 presses the sub arm 44 in theclockwise direction in FIG. 1B.

More specifically, with the pressure force from the blade return spring46, the first blade 41 and the second blade 42 travel in the directionof opening the apertures 1 a and 2 a. Furthermore, after the first blade41 and the second blade 42 have completely travelled in the direction ofopening the apertures 1 a and 2 a with the urging force from the bladereturn spring 46, the first blade 41 and the second blade 42 collidewith a blade cushioning member 4.

The blade cushioning member 4 is fixed to a shaft portion 1 h, which hasa rectangular shape and which is provided on the shutter base plate 1.The blade cushioning member 4 has a rectangular outer shape. The shaftportion 1 h has the same rectangular outer shape as the outer shape ofthe blade cushioning member 4. More specifically, when the bladecushioning member 4 is mounted on the shutter base plate 1, sides of theouter shape of the blade cushioning member 4 and sides of the shaftportion 1 h are substantially parallel to one another.

In the present exemplary embodiment, the blade cushioning member 4 andthe shaft portion 1 h have the rectangular shape. However, the bladecushioning member 4 and the shaft portion 1 h can have a polygonal shapedifferent from the rectangular shape if the polygonal shape satisfiesthe above-described condition.

The blade cushioning member 4 is made of a rubber material, such aschloroprene rubber, butyl rubber, polyurethane rubber, or siliconrubber, or a material that can absorb an impact, such as an elastomer.The blade cushioning member 4 is surrounded by and covered with a bladecontact member 5. The blade contact member 5 is made of a materialhaving a wear resistance higher than the wear resistance of the bladecushioning member 4. More specifically, the blade contact member 5 ismade of a metal material or a plastic material. The blade contact member5 is fixed on the blade cushioning member 4.

When the first blade 41 and the second blade 42 are moved in a directionof coming into collision with the blade cushioning member 4, the firstblade 41 and the second blade 42 are configured not to directly contactthe blade cushioning member 4. With the above-described configuration,abrasion of the blade cushioning member 4, which may otherwise occur ifthe first blade 41 and the second blade 42 collide with the bladecushioning member 4, is prevented.

FIGS. 2A through 2D illustrate the drive lever 11, the blade lever 15,and the ratchet 16. FIGS. 2A and 2C illustrate the drive lever 11, theblade lever 15, and the ratchet 16 viewed from the shutter base plate 1.FIG. 2B is a section A-A in FIG. 2A. More specifically, FIG. 2B is across section of an armature supporting portion 11 a of the drive lever11. FIG. 2D is a section B-B in FIG. 2C. More specifically, FIG. 2Dillustrates an exemplary relationship between a roller supporting shaft11 d of the drive lever 11 and a roller bearing portion 15 d of theblade lever 15.

Referring to FIGS. 2A and 2C, a projection portion 11 e is formed on thedrive lever 11. On the other hand, a projection portion 15 b is formedon the blade lever 15. In the state illustrated in FIG. 2A, theprojection portion 11 e contacts the projection portion 15 b. In thestate illustrated in FIG. 2C, the projection portion 11 e does notcontact the projection portion 15 b.

Referring to FIG. 2B, the armature supporting portion 11 a is providedto the drive lever 11. A through-hole 11 b is formed through thearmature supporting portion 11 a. On one end of an armature shaft 12 a,a flange 12 b, whose dimension is greater than the inner diameter of thethrough-hole 11 b, is formed.

The other end of the armature shaft 12 a is loosely inserted to thethrough-hole 11 b. After having attached the armature 12 to the armatureshaft 12 a, the other end of the armature shaft 12 a is swaged.

An armature spring 17, which is a compression spring, is provided aroundthe armature shaft 12 a and between the armature 12 and the armaturebearing portion 11 a. The armature spring 17 applies an urging force inthe direction of separating the armature 12 from the armature supportingportion 11 a. A hemisphere-shaped protrusion 11 c is formed on thearmature supporting portion 11 a at a position opposite the flange 12 b.

As illustrated in FIGS. 2A, 2C, and 2D, a roller 13 is pivotablysupported around the roller supporting shaft 11 d of the drive lever 11.Lubricating oil is applied between the roller supporting shaft 11 d andthe roller 13. The roller 13 contacts a second cam surface 22 c of thesecond cam gear 22.

The projection portion 11 e is provided to the drive lever 11. Theprojection portion 11 e contacts the projection portion 15 b of theblade lever 15. The engaging portion 15 a, which protrudes from theblade lever 15, is provided to the blade lever 15. The engaging portion15 a extends through an arc-shaped perforation 1 e of the shutter baseplate 1. In addition, the engaging portion 15 a engages into a hole 43 aof the main arm 43 on the back surface of the shutter base plate 1.

Accordingly, the main arm 43 pivots in interlock with the pivoting ofthe blade lever 15. A cam follower 15 e is provided to the blade lever15. The cam follower 15 e contacts a cam surface 21 b of the first camgear 21.

Two light shielding walls 15 c are provided to the blade lever 15. Thelight shielding walls 15 c shields the photo sensor 32 from light. Thephoto sensor 32 detects a pivoting position of the blade lever 15. Inother words, the photo sensor 32 functions as a detection unit and thelight shielding walls 15 c functions as a detection object portion.

The roller bearing portion 15 d is provided to the blade lever 15. Inorder to prevent falling off of the roller 13 from the roller supportingshaft 11 d, the roller bearing portion 15 d extends towards the rollersupporting shaft 11 d. The roller bearing portion 15 d is formed in arange in which the roller supporting shaft 11 d moves during driving ofthe blade lever 15 in the direction of opening of the apertures 1 a and2 a by the first blade 41 and the second blade 42 with the urging forcefrom the blade return spring 46.

More specifically, regardless of the positional relationship between thedrive lever 11 and the blade lever 15, the roller bearing portion 15 dis located opposite the roller supporting shaft 11 d. Accordingly, evenif the lubricating oil applied between the roller supporting shaft 11 dand the roller 13 has spread, the spread oil may only adhere to theroller bearing portion 15 d and would not spread over to the shutterbase plate 1.

Referring to FIG. 2D, a cylinder portion 11 f of the drive lever 11 fitson the shaft 1 b of the shutter base plate 1. Accordingly, the drivelever 11 is pivotably supported around the shaft 1 b of the shutter baseplate 1. Furthermore, the blade lever 15 fits in the cylinder portion 11f of the drive lever 11. Accordingly, the blade lever 15 is pivotablysupported around the cylinder portion 11 f of the drive lever 11.

With the above-described configuration, the blade lever 15 pivots inrelation to the shutter base plate 1, and the drive lever 11 pivots inrelation to the shutter base plate 1 around the same shaft as thepivoting operation of the blade lever 15.

As illustrated in FIG. 2D, a blade drive spring 14, which is a torsionspring, is provided between the ratchet 16 and the drive lever 11. Oneend 14 a of the blade drive spring 14 is retained by the drive lever 11.The other end 14 b of the blade drive spring 14 is retained by theratchet 16.

In FIG. 2A, the blade drive spring 14 presses the drive lever 11 in thecounterclockwise direction. The free length of the blade drive spring 14is designed to be longer than the interval between the drive lever 11and the ratchet 16. The blade drive spring 14 functions as a pressurespring. Furthermore, the blade drive spring 14 urges the blade drivespring 14 against the shutter base plate 1.

As illustrated in FIG. 2D, a slope 15 f is provided to the blade lever15. With the slope 15 f, the roller bearing portion 15 d of the bladelever 15 extends away from the pivot center of the blade lever 15 in asubstantially conic shape. If the slope 15 f is otherwise provided toextend away from the pivot center of the blade lever 15 in asubstantially cylindrical shape, the inertial force applied on the bladelever 15 when the blade lever 15 pivots may become excessively great.

To prevent the above-described problem of an excessively great inertialforce applied to the blade lever 15, in the present exemplaryembodiment, the roller bearing portion 15 d is designed to have asubstantially conic shape. Accordingly, the roller bearing portion 15 dcan be provided while preventing a very great inertial force on theblade lever 15.

The drive lever 11 is assembled to the blade lever 15 in the followingmanner. First, the roller 13 is inserted into the roller supportingshaft 11 d. Subsequently, the blade lever 15 is inserted into thecylinder portion 11 f in the state illustrated in FIG. 2A. Then theblade lever 15 is turned in the counterclockwise direction in relationto the drive lever 11, the relationship between the blade lever 15 andthe drive lever 11 becomes the state illustrated in FIG. 2C.

In the state illustrated in FIG. 2C, the roller supporting shaft 11 d islocated between the roller bearing portion 15 d and the light shieldingwalls 15 c. Accordingly, falling off of the drive lever 11 from theblade lever 15 is always prevented.

In addition, the dimension of the range in which the roller supportingshaft 11 d moves between the roller bearing portion 15 d and the lightshielding wall 15 c is smaller than the thickness of the roller 13.Accordingly, falling off of the roller 13 from the roller supportingshaft 11 d is always prevented.

As described above, in the state in which the drive lever 11, the roller13, and the blade lever 15 are integrally operated, the cylinder portion11 f of the drive lever 11 is fitted on the shaft 1 b of the shutterbase plate 1.

FIG. 3 illustrates a state in which the blade drive spring 14 and theratchet 16 are assembled to the drive lever 11. Referring to FIG. 3, oneend 14 a of the blade drive spring 14 is retained by the drive lever 11and the other end 14 b of the blade drive spring 14 engages a slit 16 b,which is provided to the ratchet 16.

In the state illustrated in FIG. 3, the blade drive spring 14 is in a“free” state, in which the blade drive spring 14 has not been charged.When the ratchet 16 is turned in the clockwise direction, the bladedrive spring 14 is charged. In the state in which the ratchet 16 isturned to charge the blade drive spring 14, the engaging claw portion 31b, which is provided to the auxiliary base plate 31, engages the ratchettooth 16 a.

The urging force from the blade drive spring 14 against the drive lever11 is adjusted by adjusting the turning amount of the ratchet 16. Inother words, the ratchet 16 is equivalent to a ratchet member.

FIGS. 4A through 4C illustrate the ratchet 16. FIG. 4A illustrates anouter appearance of the ratchet 16. Referring to FIG. 4A, the ratchet 16has a duplex cylinder-shape formed by a first cylinder portion 16 c anda second cylinder portion 16 d.

The ratchet teeth 16 a are provided to the outer circumferential surfaceof the first cylinder portion 16 c. The second cylinder portion 16 d,which is a cylindrical portion concentric with the first cylinderportion 16 c, is provided inside the first cylinder portion 16 c. Theslit 16 b is provided to the first cylinder portion 16 c as a notch thatis cut at a part of the first cylinder portion 16 c.

At an end of the slit 16 b, a projection portion 16 e, which protrudesfrom the inner peripheral surface of the first cylinder portion 16 ctowards the second cylinder portion 16 d, is provided. Accordingly, theportion at which the projection portion 16 e is formed has a thicknessthicker than the other portion of the first cylinder portion 16 c in thedirection of the diameter of the first cylinder portion 16 c.

A protrusion 16 f, which protrudes towards the first cylinder portion 16c, is provided in a portion of the second cylinder portion 16 d on theouter peripheral surface thereof in which the slit 16 b and theprojection portion 16 e are located opposite each other.

FIG. 4B illustrates a state in which the blade drive spring 14 isprovided between the first cylinder portion 16 c and the second cylinderportion 16 d and the other end 14 b of the blade drive spring 14 engagesthe slit 16 b.

In the state illustrated in FIG. 4B, the blade drive spring 14 is in thefree state, in which the blade drive spring 14 has not been charged.

Referring to FIG. 4B, in a range of a first angular position P1 of anend 16 b 1 of the slit 16 b from a position of the end 16 b 1 in theclockwise direction, the projection portion 16 e, which protrudes fromthe inner peripheral surface of the first cylinder portion 16 c towardsthe second cylinder portion 16 d, is formed. More specifically, theprojection portion 16 e is formed in the range in which the end 16 b 1is located at the first angular position P1 in a direction opposite thedirection of charging the blade drive spring 14, from the end 16 b 1 ofthe slit 16 b, with which the other end 14 b of the blade drive spring14 contacts, in turning the ratchet 16 in the direction of charging theblade drive spring 14.

A thickness Ha of the edge 16 b 1 of the slit 16 b is thicker than athickness Hb of an edge 16 b 2 of the slit 16 b. The end 16 b 1 of theslit 16 b is equivalent to one end of the slit 16 b and the edge 16 b 2of the slit 16 b is equivalent to the other end of the slit 16 b. Theslit 16 b is formed so that the end 16 b 1 of the slit 16 b becomes atip of the ratchet tooth 16 a. With the above-described configuration,the area of the end 16 b 1 of the slit 16 b can become as large aspossible.

When the ratchet 16 is turned in the counterclockwise direction from thestate illustrated in FIG. 4B, one end 14 a of the blade drive spring 14contacts the end 16 b 1 of the slit 16 b. In this state, the blade drivespring 14 is charged. When the blade drive spring 14 is charged, thestate of the blade drive spring 14 becomes the state illustrated in FIG.4C.

When the blade drive spring 14 is charged, a force acts on the end 16 b1 of the slit 16 b. Although the ratchet 16 is made of a resin material,the end 16 b 1 of the slit 16 b has a sufficient strength due to theprojection portion 16 e formed thereto. Accordingly, in charging theblade drive spring 14, one end 14 a of the blade drive spring 14 maynever be pressed into the end 16 b 1 of the slit 16 b.

Referring to FIG. 4C, when the blade drive spring 14 is charged, theblade drive spring 14 is squeezed to be in a tensioned state. In thisstate, the diameter of the blade drive spring 14 varies from a diameterDa (FIG. 4B) to a diameter Db (FIG. 4C).

When the diameter of the blade drive spring 14 becomes smaller, therange of the contact between one end 14 a of the blade drive spring 14and the end 16 b 1 of the slit 16 b may become smaller. If one end 14 aof the blade drive spring 14 is designed to be long to prevent theabove-described problem, if the amount of charge on the blade drivespring 14 is not large, one end 14 a of the blade drive spring 14 may beprojected from the slit 16 b.

In this case, the total size of the shutter device cannot be effectivelyreduced because no part can be provided in a space in which one end 14 aof the blade drive spring 14 may be projected. In order to prevent theabove-described problem, in the present exemplary embodiment, aprojection portion 16 f, which protrudes towards the first cylinderportion 16 c, is provided to the outer peripheral surface of the secondcylinder portion 16 d in a range in which the projection portion 16 e isformed and located at the first angular position P1 from a position P2of the other end 16 b 2 of the slit 16 b.

The blade drive spring 14 is charged in the above-described manner. Evenif the diameter of the blade drive spring 14 has become the diameter Dbillustrated in FIG. 4C, the range of contact between one end 14 a of theblade drive spring 14 and the end 16 b 1 of the slit 16 b can besecured.

Accordingly, the problem of one end 14 a of the blade drive spring 14being pressed into the end 16 b 1 of the slit 16 b, which may otherwiseoccur if the range of contact between one end 14 a of the blade drivespring 14 and the end 16 b 1 of the slit 16 b becomes small, may neverarise. In addition, it is not necessary to provide long one end 14 a ofthe blade drive spring 14. Accordingly, the reduction of the size of theshutter device may not be hindered.

FIGS. 5A and 5B illustrate the first cam gear 21 and the second cam gear22. A gear 21 a and a cam 21 b are provided to the first cam gear 21.The gear 21 a engages a gear 22 b of the second cam gear 22.Accordingly, the rotation of the first cam gear 21 is transmitted to thesecond cam gear 22. The gear 21 a functions as a first gear portion. Thegear 22 b functions as a second gear portion.

The cam 21 b is a cam traced by a cam follower 15 e of the blade lever15. In the state illustrated in FIG. 5A, the cam 21 b and the camfollower 15 e contact each other. In this state, a counterclockwiseforce from the blade return spring 46 is applied to the blade lever 15but the pivoting operation of the blade lever 15 is prevented by thecontact between the cam 21 b and the cam follower 15 e. Accordingly, thefirst cam gear 21 retains the blade lever 15 to close the apertures 1 aand 2 a by the first blade 41 and the second blade 42.

In the state illustrated in FIG. 5B, the first cam gear 21 is rotated inthe counterclockwise direction from the state illustrated in FIG. 5A.Furthermore, in the state illustrated in FIG. 5B, the cam 21 b isdetached from the cam follower 15 e. Furthermore, the blade lever 15 ispivoted by the blade return spring 46 in the counterclockwise direction.

When the first cam gear 21 is rotated in the counterclockwise directionfrom the state illustrated in FIG. 5B, the cam 21 b contacts the camfollower 15 e and the blade lever 15 is pivoted in the clockwisedirection. In the above-described manner, the blade return spring 46 ischarged.

The phase armature 23 is provided on the bottom surface of the camportion 21 b. The phase armature 23 contacts a pattern portion 38 c ofthe FPC 38. The phase armature 23 detects a rotation phase of the firstcam gear 21.

A first cam 22 a, the gear 22 b, and the second cam 22 c are provided tothe second cam gear 22. The gear 22 b engages a transmission gear (notillustrated). Accordingly, a drive force from a motor (not illustrated)is transmitted via the transmission gear.

The gear 22 b has the same number of teeth as the number of teeth of thegear 21 a. The gear 22 b and the gear 21 a engage each other at apredetermined phase. Accordingly, the first cam gear 21 and the secondcam gear 22 rotate at the predetermined phase and with the same rotationfrequency.

The first cam 22 a, which a first cam portion, contacts a cam follower36 a of the mirror lever 36. The first cam 22 a causes the mirror lever36 to pivot between the mirror-up position and the mirror-down position.More specifically, the second cam gear 22 descends the main mirror 6downwards into the photographic optical path when the first cam 22 a andthe cam follower 36 a of the mirror lever 36 contact each other at afirst position. In addition, the second cam gear 22 ascends, causing themain mirror 6 to retract from the photographic optical path when thefirst cam 22 a and the cam follower 36 a of the mirror lever 36 aredetached from each other at a second position. The second cam 22 c,which is a second cam portion, contacts the stored roller 13 retained bythe drive lever 11. The second cam 22 c functions to charge anddischarge the drive lever 11.

FIG. 6 is a timing chart illustrating timings of operations of themirror lever 36, the main mirror 6, the blade lever 15, the drive lever11, the coil 34, the blade group, and the image sensor 116. Operationsexecuted by the shutter unit 100 during a time period from a state A toa state M illustrated in FIG. 6 will be described in detail below withreference to FIGS. 7A through 7C, 15A, and 15B.

The state A illustrated in FIG. 6 is a pre-release standby state. FIGS.7A through 7C illustrate states of the shutter unit 100 in thepre-release standby state. FIG. 7A illustrates the shutter unit 100viewed from the main mirror 6. FIG. 7B illustrates the shutter unit 100viewed from the image sensor 116.

In FIGS. 7A through 7C, the shutter base plate 1, the cover plate 2, andthe auxiliary base plate 31 are omitted for easier understanding ofoperations of the cam gears and the levers. In the pre-release standbystate, the first cam gear 21 and the second cam gear 22 are stopped ateach corresponding position illustrated in FIGS. 7A and 7B.

The roller 13, which is retained by the drive lever 11, contacts the camtop portion 22 d of the second cam 22 c of the second cam gear 22. Inthe state illustrated in each of FIGS. 7A and 7B, the drive lever 11 hasovercharged the blade drive spring 14. In the state in which the bladedrive spring 14 has been overcharged, the drive lever 11 has been movedin the direction of charging the blade drive spring 14 over a positionat which the yoke 33 can retain the armature 12 when the coil 34 hasbeen energized.

Referring to FIG. 7C, in the overcharged state, the armature 12 contactsthe yoke 33. In addition, in this state, the armature supporting portion11 a of the blade drive member (the drive lever 11) compresses thearmature spring 17. Accordingly, the flange 12 b of the armature 12 isseparated from the protrusion 11 c of the drive lever 11. The camfollower 15 e of the blade lever 15 contacts the cam top 21 c of the cam21 b of the first cam gear 21. As described above, the blade lever 15 islocked in the state illustrated in FIG. 7B.

Referring to FIG. 7B, the blade return spring 46 presses the sub arm 44in the clockwise direction but the blade lever 15 has been locked.Accordingly, the first blade 41 and the second blade 42 are retainedagainst the urging force from the blade return spring 46 in the state inwhich the apertures 1 a and 2 a are closed.

In this state, the roller bearing portion 15 d of the blade lever 15 islocated opposite the roller 13 to prevent falling off of the roller 13from the roller supporting shaft 11 d. The cam follower 36 a of themirror lever 36 contacts a cam top portion 22 e of the first cam 22 a ofthe second cam gear 22. As illustrated in FIG. 7A, the mirror lever 36retains the mirror lever drive spring 39 while charging the mirror leverdrive spring 39.

The main mirror 6 is pressed by the main mirror drive spring 7 in themirror-down direction. The main mirror 6 becomes the mirror-down statewhen the main mirror 6 contacts a stopper (not illustrated). In thisstate, a gap is formed between the shaft portion 6 a of the main mirror6 and a contact portion 36 b of the mirror lever 36.

With the above-described configuration, the main mirror 6 can bepositioned by the stopper (not illustrated) at a correct position evenif any error has occurred in positioning the mirror lever 36.

If a release signal is input in the pre-release standby state, the coil34 is energized and the yoke 33 attracts the armature 12. At the sametime, when the motor (not illustrated) is energized and the first camgear 21 and the second cam gear 22 are rotated, the blade lever isunlocked (a state B illustrated in FIG. 6). In the state B illustratedin FIG. 6, the blade lever has been unlocked.

FIGS. 8A through 8C illustrate exemplary states in the state in whichthe blade lever has been unlocked. FIG. 8A illustrates the shutter unit100 viewed from the main mirror 6. FIG. 8B illustrates the shutter unit100 viewed from the image sensor 116.

In FIGS. 8A through 8C, the shutter base plate 1, the cover plate 2, andthe auxiliary base plate 31 are omitted for easier understanding ofoperations of the cam gears and the levers. In the blade lever unlockedstate, the first cam gear 21 and the second cam gear 22 are stopped ateach corresponding position illustrated in FIGS. 8A and 8B.

In the following description, states different from the pre-releasestandby state illustrated in FIGS. 7A through 7C only will be describedand the state that does not change from the pre-release standby statewill not be described in detail.

When the motor (not illustrated) is energized, the first cam gear 21 isrotated from the state illustrated in FIGS. 7A and 7B to the stateillustrated in FIGS. 8A and 8B. When the first cam gear 21 is rotated tobe in the state illustrated in FIGS. 8A and 8B, the cam follower 15 e ofthe blade lever 15 is detached from the cam top 21 c of the cam 21 b ofthe first cam gear 21. To paraphrase this, the cam 21 b retracts from apivoting locus of the cam follower 15 e of the blade lever 15 to unlockthe blade lever 15. As a result, the blade lever 15 shifts to a state inwhich the blade lever 15 can pivot around the shaft 1 b.

When the blade lever 15 is unlocked, the first blade 41 and the secondblade 42 travel in the direction of opening the apertures 1 a and 2 adue to the urging force from the blade return spring 46, which pressesthe sub arm 44. Following the above-described operation, the blade lever15 pivots around the shaft 1 b.

At the same time, the roller 13, which is mounted on the rollersupporting shaft 11 d of the drive lever 11, moves along the rollerbearing portion 15 d of the blade lever 15 without being disengaged fromthe roller supporting shaft 11 d. In the blade lever unlocked state, asillustrated in FIGS. 8A and 8B, after the first blade 41 and the secondblade 42 have travelled in the direction of opening the aperture 1 a andthe aperture 2 a, the first blade 41 and the second blade 42 collidewith the blade cushioning member 4 in a mutually overlapped state.

The blade cushioning member 4 alleviates the impact that acts on thefirst blade 41 and the second blade 42 when the first blade 41 and thesecond blade 42 have completely travelled. The blade cushioning member 4is surrounded by and covered with the blade contact member 5.

More specifically, when the first blade 41 and the second blade 42collide with the blade cushioning member 4 in the mutually overlappedstate, the blade contact member 5 is located between the blade groupincluding the first blade 41 and the second blade 42 and the bladecushioning member 4. The blade contact member 5 is made of a materialhaving a wear resistance higher than the wear resistance of the bladecushioning member 4.

When the first blade 41 and the second blade 42 collide with the bladecushioning member 4, the first blade 41 and the second blade 42 directlycontact the blade contact member 5 without directly contacting the bladecushioning member 4. Because the blade contact member 5 is made of amaterial having a high wear resistance, such as a metal material, dustparticles that may be generated due to wear may hardly be generated evenwhen the first blade 41 and the second blade 42 directly contact theblade contact member 5.

Because the first blade 41 and the second blade 42 do not directlycontact the blade cushioning member 4, the blade cushioning member 4 canbe made of a material having a high impact absorption performance evenif dust particles may be easily generated even if the first blade 41 andthe second blade 42 should collide with the blade cushioning member 4.

As illustrated in FIGS. 8A and 8B, when the first blade 41 and thesecond blade 42 contact the blade contact member 5, a gap is formedbetween the projection portion 11 e and the projection portion 15 b ofthe blade lever 15 as illustrated in FIG. 8C. In the example illustratedin FIG. 7C, the blade drive spring 14 has been overcharged. If the firstblade 41 and the second blade 42 travel in the direction of opening theapertures 1 a and 2 a due to the urging force from the blade returnspring 46 in the overcharged state, the blade lever 15 never contactsthe drive lever 11.

Accordingly, the impact arising when the first blade 41 and the secondblade 42 travel in the direction of opening the apertures 1 a and 2 adue to the urging force from the blade return spring 46 is nevertransmitted to the drive lever 11.

In the state in which the blade drive spring 14 has been overcharged,the drive lever 11 has pressed the armature 12 against the yoke 33. Ifan impact is applied to the drive lever 11 in this state, the armature12 and an attraction force receiving surface of the yoke 33 may bedamaged.

Any damage on the armature 12 and the attraction force receiving surfaceof the yoke 33 may degrade the accuracy of exposure. The presentexemplary embodiment can prevent the damage on the armature 12 and theattraction force receiving surface of the yoke 33 as described above.

When the first blade 41 and the second blade 42 travel in the directionof opening the apertures 1 a and 2 a due to the urging force from theblade return spring 46 and contact the blade contact member 5, the firstblade 41 and the second blade 42 hop as illustrated in FIG. 6.

When the state shifts from the pre-release standby state to the bladelever unlocked state, the second cam gear 22 rotates as the first camgear 21 rotates. As illustrated in FIG. 8A, on the second cam gear 22,the cam follower 36 a of the mirror lever 36 contacts the cam topportion 22 e of the first cam 22 a of the second cam gear 22.

Accordingly, similarly to the state illustrated in FIG. 7A, the mirrorlever 36 is retained in the state in which the mirror lever drive spring39 has been charged. In addition, the main mirror 6, similarly to thestate illustrated in FIG. 7A, is pressed by the main mirror drive spring7 in the mirror-down direction to shift to the mirror-down state bycontacting the stopper (not illustrated). More specifically, the firstblade 41 and the second blade 42 shift to the state of opening theapertures 1 a and 2 a but the main mirror 6 remains to be in themirror-down state.

When the motor (not illustrated) is continuously energized, the firstcam gear 21 and the second cam gear 22 are rotated and the state shiftsto a mirror lever unlocked state illustrated in FIG. 6. In FIG. 6, astate C illustrates the mirror lever unlocked state.

The first cam gear 21 and the second cam gear 22 further rotate from thestate illustrated in FIG. 6. When the second cam gear 22 rotates, thecam follower 36 a of the mirror lever 36 is detached from the first cam22 a of the second cam gear 22.

After the first cam 22 a has retracted from the pivoting locus of thecam follower 36 a, the mirror lever 36 is unlocked. In addition, themirror lever 36 is turned by the urging force from the mirror leverdrive spring 39 in the clockwise direction in FIG. 8A.

In the pre-release standby state, a gap is formed between the shaftportion 6 a of the main mirror 6 and the contact portion 36 b of themirror lever 36. Accordingly, after the mirror lever 36 has been turnedin the clockwise direction in FIG. 8A by an amount equivalent to thegap, the contact portion 36 b of the mirror lever 36 contacts the shaftportion 6 a of the main mirror 6.

When the contact portion 36 b of the mirror lever 36 contacts the shaftportion 6 a of the main mirror 6, the state shifts to a state D (FIG.6), which is equivalent to a mirror lever contact state. In the mirrorlever contact state, the contact portion 36 b of the mirror lever 36contacts the shaft portion 6 a of the main mirror 6. In addition, inthis state, the mirror lever 36 starts pivoting the main mirror 6 in themirror-up direction against the urging force from the main mirror drivespring 7.

When the main mirror 6 contacts the stopper (not illustrated), the mainmirror 6, as illustrated in FIG. 6, stops at the mirror-up positionafter a hopping action. In order to reduce the time of hopping of themain mirror 6, the mirror lever drive spring 39 is provided with arelatively great spring force.

Accordingly, the time of hopping of the main mirror 6 becomes shorterthan the time of hopping of the first blade 41 and the second blade 42in the blade lever unlocked state. When the hopping of the main mirror 6ends, the main mirror 6 shifts to a state E (FIG. 6), which isequivalent to a mirror-up live view state. The state E illustrated inFIG. 6 illustrates the mirror-up live view state.

FIGS. 9A and 9B illustrate states of the shutter unit 100 in themirror-up live view state. FIG. 9A illustrates the shutter unit 100viewed from the main mirror 6. FIG. 9B illustrates the shutter unit 100viewed from the image sensor 116.

In FIGS. 9A and 9B, the shutter base plate 1, the cover plate 2, and theauxiliary base plate 31 are omitted for easier understanding ofoperations of the cam gears and the levers. In the mirror-up live viewstate, the first cam gear 21 and the second cam gear 22 are stopped ateach corresponding position illustrated in FIGS. 9A and 9B.

The drive lever 11 and the blade lever 15 are in each correspondingstate similar to the state illustrated in FIGS. 8A and 8B. Morespecifically, the first blade 41 and the second blade 42 are in thestate in which the first blade 41 and the second blade 42 travel to openthe apertures 1 a and 2 a to contact the blade contact member 5 in thisstate.

In the mirror-up live view state, the retained roller 13, which isretained by the drive lever 11, contacts the cam top portion 22 d of thesecond cam 22 c of the second cam gear 22. Accordingly, in this state,the blade drive spring 14 is overcharged.

Accordingly, in the mirror-up live view state, a gap is formed betweenthe projection portion 11 e of the drive lever 11 and the projectionportion 15 b of the blade lever 15 as illustrated in FIG. 8C. Inaddition, as described above, the cam follower 36 a of the mirror lever36 is detached from the first cam 22 a of the second cam gear 22.Furthermore, the mirror lever 36 is turned by the urging force from themirror lever drive spring 39.

In addition, the mirror lever 36 pivots the main mirror 6 in themirror-up direction against the urging force from the main mirror drivespring 7. If the motor (not illustrated) is stopped in this state, alight flux from the interchangeable lens 201 reaches the image sensor116. In addition, the state of the imaging apparatus shifts to a liveview state, in which an object image captured by the image sensor 116 isdisplayed on a display monitor.

In the mirror-up live view state, the roller 13, which is retained bythe drive lever 11, contacts the cam top portion 22 d of the second cam22 c of the second cam gear 22. Accordingly, if the energization of thecoil 34 is discontinued, the first blade 41 and the second blade 42remain in the state in which the first blade 41 and the second blade 42have travelled to open the apertures 1 a and 2 a.

The motor (not illustrated) is energized in the mirror-up live viewstate to rotate the first cam gear 21 and the second cam gear 22. Thenin a state F (FIG. 6), which illustrates an unset state, the motor isstopped. The state F illustrated in FIG. 6 corresponds to the unsetstate.

FIGS. 10A through 10D illustrate a state in which the shutter unit 100is in the unset state. FIG. 10A illustrates the shutter unit 100 viewedfrom the main mirror 6. FIG. 10B illustrates the shutter unit 100 viewedfrom the image sensor 116.

In FIGS. 10A and 10B, the shutter base plate 1, the cover plate 2, andthe auxiliary base plate 31 are omitted for easier understanding ofoperations of the cam gears and the levers. In the unset state, thefirst cam gear 21 and the second cam gear 22 are stopped at eachcorresponding position illustrated in FIGS. 10A and 10B.

In the unset state, when the second cam gear 22 rotates, the roller 13,which is retained by the drive lever 11, is detached from the cam topportion 22 d of the second cam 22 c of the second cam gear 22.Accordingly, the drive lever 11 pivots in the clockwise direction ofFIG. 10A due to the urging force from the blade drive spring 14. Inaddition, the overcharging of the blade drive spring 14 is discharged.

Even after the roller 13 is detached from the second cam gear 22 d ofthe second cam 22 c, the armature 12 is attracted by the yoke 33 becausethe coil 34 has been continuously energized. In addition, the firstblade 41 and the second blade 42 remain in the state in which theapertures 1 a and 2 a are opened.

After the overcharging of the blade drive spring 14 is discharged, theflange 12 b of the armature 12 contacts the protrusion 11 c of the bladedrive member (the drive lever 11) due to the urging force from thearmature spring 17. Accordingly, as illustrated in FIG. 10C, the drivelever 11 slightly pivots and the projection portion 11 e of the drivelever 11 contacts the projection portion 15 b of the blade lever 15.

Referring to FIG. 10D, when the projection portion 11 e of the drivelever 11 presses the projection portion 15 b of the blade lever 15, thefirst blade 41 and the second blade 42 are detached from the bladecontact member 5. More specifically, when the coil 34 is energized inthe state in which the blade drive spring 14 is overcharged, the yoke 33attracts the armature 12. In addition, the blade lever 15 contacts thedrive lever 11 before the overcharging of the blade drive spring 14 isdischarged.

In the unset state, similar to the state of the main mirror 6 in themirror-up live view state, the main mirror 6 is stopped at the mirror-upposition. As illustrated in FIG. 6, an imaging and exposure operationstarts when a pixel resetting scan operation on the image sensor 116(hereinafter simply referred to as an “electronic first curtaintravelling”) is executed in the unset state.

Time from a timing of input of a release signal to a timing of start ofthe electronic first curtain travelling corresponds to a release timelag. In the present exemplary embodiment, the operation by the firstblade 41 and the second blade 42 for opening the apertures 1 a and 2 a,whose hopping time is relatively long, is started before executing themirror-up operation of the main mirror 6, whose hopping time isrelatively short.

If the opening operation by the first blade 41 and the second blade 42and the mirror-up operation for ascending the main mirror 6 aresimultaneously started, the electronic first curtain travelling cannotbe started until the hopping of the first blade 41 and the second blade42 ends even if the hopping of the main mirror 6 has ended. As a result,the release time lag may become long.

In the present exemplary embodiment, the operation for ascending themain mirror 6 to the mirror-up state is started after the openingoperation by the first blade 41 and the second blade 42 is started toprevent the above-described problem. In addition, in the presentexemplary embodiment, by starting the operation for ascending the mainmirror 6 to the mirror-up state after the opening operation by the firstblade 41 and the second blade 42 is started, the threat of exposure tothe first blade 41 and the second blade 42 to direct sunlight can bereduced.

With the above-described configuration, the damage that may occur if thefirst blade 41 and the second blade 42 are exposed to direct sunlightcan be reduced if the first blade 41 and the second blade 42 made of aPET material containing a blackening are used.

By stopping the energization of the coil 34 after a time intervalcorresponding to a set shutter speed has elapsed after the electronicfirst curtain travelling has started, the state shifts to a state G(FIG. 6), which illustrates a blade travelling state. The state Gillustrated in FIG. 6 corresponds to the blade travelling state.

FIGS. 11A and 11B illustrate states of the shutter unit 100 in the bladetravelling state. FIG. 11A illustrates the shutter unit 100 viewed fromthe main mirror 6. FIG. 11B illustrates the shutter unit 100 viewed fromthe image sensor 116. In FIGS. 11A and 11B, the shutter base plate 1,the cover plate 2, and the auxiliary base plate 31 are omitted foreasier understanding of operations of the cam gears and the levers.

As illustrated in FIGS. 11A and 11B, when the energization of the coil34 is discontinued, the first blade 41 and the second blade 42 cannotremain in the state in which the apertures 1 a and 2 a remain opened.The drive lever 11 pivots as illustrated in FIGS. 11A and 11B due to theurging force from the blade drive spring 14.

When the drive lever 11 is pivoted, the projection portion 11 e of thedrive lever 11 presses the projection portion 15 b of the blade lever15. Accordingly, the blade lever 15 also is pivoted. With the integratedoperation of the drive lever 11 and the blade lever 15, the first blade41 and the second blade 42 travel in the direction of closing theapertures 1 a and 2 a against the urging force from the blade returnspring 46. In the unset state illustrated in FIGS. 10A through 10D, theprojection portion 11 e of the drive lever 11 has already contacted theprojection portion 15 b of the blade lever 15.

When the energization of the coil 34 is discontinued, the drive lever 11and the blade lever 15 integrally pivot due to the urging force from theblade drive spring 14. More specifically, in the present exemplaryembodiment, when the first blade 41 and the second blade 42 havetravelled in the direction of closing the apertures 1 a and 2 a, thedrive lever 11 and the blade lever 15 integrally pivot even from thestart of the travel of the first blade 41 and the second blade 42.

In the middle of travelling the first blade 41 and the second blade 42in the direction of closing the apertures 1 a and 2 a, the projectionportion 11 e of the drive lever 11 may collide with the projectionportion 15 b of the blade lever 15 before the integral pivotingoperation of the drive lever 11 and the blade lever 15. However, in thiscase, the pivot speed may vary across the timing of collision with 115.As a result, the accuracy of travel of the first blade 41 and the secondblade 42 may degrade.

In the present exemplary embodiment, before travelling the first blade41 and the second blade 42, the drive lever 11 and the blade lever 15are integrated together. In addition, during the travel of the firstblade 41 and the second blade 42, the drive lever 11 and the blade lever15 integrally pivot.

Accordingly, the pivoting speed of the drive lever 11 and the bladelever 15 becomes stabilized. In addition, the first blade 41 and thesecond blade 42 can travel with a high accuracy. In addition, with theintegrated pivoting operation of the drive lever 11 and the blade lever15, the relative positions of the roller 13, which is mounted on theroller supporting shaft 11 d of the drive lever 11, and the rollerbearing portion 15 d of the blade lever 15 may not vary.

With the above-described configuration, no friction may arise betweenthe roller 13 and the roller bearing portion 15 d during the travel ofthe first blade 41 and the second blade 42 in the direction of closingthe apertures 1 a and 2 a. In addition, coefficients of friction may notvary because the relative positions of the roller 13 and the rollerbearing portion 15 d may not vary even if the direction of gravityacting on the roller due to a change of orientation of the imagingapparatus.

With the above-described configuration, the present exemplary embodimentcan reduce the friction that may arise when the first blade 41 and thesecond blade 42 travel in the direction of closing the apertures 1 a and2 a. In addition, in the present exemplary embodiment, the first blade41 and the second blade 42 can travel with a high accuracy.

When the first blade 41 and the second blade 42 are travelled to theposition of closing the apertures 1 a and 2 a, the state shifts to astate H (FIG. 6), which illustrates a blade travel complete state. Thestate H illustrated in FIG. 6 corresponds to the blade travel completestate.

FIGS. 12A and 12B illustrate states of the shutter unit 100 in the bladetravel complete state. FIG. 12A illustrate the shutter unit 100 viewedfrom the main mirror 6. FIG. 12B illustrates the shutter unit 100 viewedfrom the image sensor 116. In FIGS. 12A through 12C, the shutter baseplate 1, the cover plate 2, and the auxiliary base plate 31 are omittedfor easier understanding of operations of the cam gears and the levers.

When the engaging portion 15 a, which is provided to the blade lever 15,collides with the semicircular cushioning member 3, which is providedover the perforation le, which is provided to the shutter base plate 1,the first blade 41 and the second blade 42 stop at the position ofclosing the apertures 1 a and 2 a.

In this state, the projection portion 11 e of the drive lever 11contacts the projection portion 15 b of the blade lever 15. In thepresent exemplary embodiment, when the first blade 41 and the secondblade 42 are travelled in the direction of closing the apertures 1 a and2 a, the drive lever 11 and the blade lever 15 are integrally pivotedall through the time of travel of the first blade 41 and the secondblade 42 from the beginning to the end thereof.

In the blade travel complete state illustrated in FIGS. 12A and 12B,when the first blade 41 and the second blade 42 travel to close theapertures 1 a and 2 a, the blade return spring 46 is charged. Inaddition, in the blade travel complete state, the photo sensor 32, whichis provided to the auxiliary base plate 31, detects that the blade lever15 has come to the pivoted position of the complete travel of theblades.

The motor (not illustrated) is energized after a predetermined time haselapsed since the energization of the coil 34 is stopped. When the motoris energized and the first cam gear 21 and the second cam gear 22rotate, the state of the imaging apparatus becomes a state I (FIG. 6),which illustrates a mirror lever charging state. The state I illustratedin FIG. 6 corresponds to the mirror lever charging state.

When the first cam gear 21 and the second cam gear 22 rotate from thestate illustrated in FIGS. 12A and 12B, the first cam 22 a of the secondcam gear 22 contacts the cam follower 36 a of the mirror lever 36. Themirror lever 36 pivots in the counterclockwise direction in FIG. 12A tocharge the mirror lever drive spring 39.

When the mirror lever 36 pivots in the counterclockwise direction inFIG. 12A, the main mirror 6 turns in the mirror-down direction due tothe urging force from the main mirror drive spring 7.

In the mirror lever charging state, similarly to the blade travelcomplete state, the first blade 41 and the second blade 42 remainstopped at the position of closing the apertures 1 a and 2 a. If themotor (not illustrated) is continuously energized in the mirror levercharging state, the first cam gear 21 and the second cam gear 22 furtherrotate. As a result, the state of the imaging apparatus shifts to astate J (FIG. 6), which illustrates a mirror lever charge completestate. The state J illustrated in FIG. 6 corresponds to the mirror levercharge complete state.

FIGS. 13A and 13B illustrate states of the shutter unit 100 in themirror lever charge complete state. FIG. 13A illustrates the shutterunit 100 viewed from the main mirror 6. FIG. 13B illustrates the shutterunit 100 viewed from the image sensor 116. In FIGS. 13A through 13C, theshutter base plate 1, the cover plate 2, and the auxiliary base plate 31are omitted for easier understanding of operations of the cam gears andthe levers.

When the second cam gear 22 rotates in the counterclockwise direction inFIG. 13A from the mirror lever charging state, the mirror lever 36charges the mirror lever drive spring 39. When the mirror lever 36 isturned as described above, the main mirror 6 is further turned in themirror-down direction. Moreover, the main mirror 6 contacts the stopper(not illustrated) and stops there.

After the main mirror 6 has stopped at the mirror-down position, thesecond cam gear 22 continues its rotation. Accordingly, the cam follower36 a of the mirror lever 36 reaches the cam top the position 22 e of thefirst cam 22 a of the second cam gear 22.

In this state, a gap is formed between the shaft portion 6 a of the mainmirror 6 and the contact portion 36 b of the mirror lever 36 asillustrated in FIG. 13A. As a result, the main mirror 6 is retained bythe stopper (not illustrated) at the correct position even if any errorhas occurred in positioning the mirror lever 36.

When the motor (not illustrated) is continuously energized in the mirrorlever charge complete state, the first cam gear 21 and the second camgear 22 further rotate. Accordingly, the state of the imaging apparatusshifts to a state K (FIG. 6), which illustrates a blade lever lockenabled state. The state K illustrated in FIG. 6 corresponds to theblade lever lock enabled state.

FIGS. 14A and 14B illustrate states of the shutter unit 100 in the bladelever lock enabled state. FIG. 14A illustrates the shutter unit 100viewed from the main mirror 6. FIG. 14B illustrates the shutter unit 100viewed from the image sensor 116. In FIGS. 14A through 14C, the shutterbase plate 1, the cover plate 2, and the auxiliary base plate 31 areomitted for easier understanding of operations of the cam gears and thelevers.

When the first cam gear 21 rotates, the cam 21 b of the first cam gear21 moves to a position at which the cam follower 15 e of the blade lever15 can contact the cam 21 b. In the blade lever lock enabled stateillustrated in FIGS. 14A and 14B, the projection portion 11 e of thedrive lever 11 keeps pressing the projection portion 15 b of the bladelever 15 due to the urging force from the blade drive spring 14.Accordingly, the cam follower 15 e of the blade lever 15 does notcontact the cam 21 b of the first cam gear 21.

When the motor (not illustrated) is continuously energized in the bladelever lock enabled state, the first cam gear 21 and the second cam gear22 rotate. Accordingly, the state of the imaging apparatus shifts to astate L (FIG. 6), which illustrates a drive lever charging state. Thestate L illustrated in FIG. 6 corresponds to the drive lever chargingstate.

FIGS. 15A and 15B illustrate states of the shutter unit 100 in the drivelever charging state. FIG. 15A illustrates the shutter unit 100 viewedfrom the main mirror 6. FIG. 15B illustrates the shutter unit 100 viewedfrom the image sensor 116. In FIGS. 15A through 15C, the shutter baseplate 1, the cover plate 2, and the auxiliary base plate 31 are omittedfor easier understanding of operations of the cam gears and the levers.

When the second cam gear 22 rotates, the second cam 22 c of the secondcam gear 22 presses the retained roller 13, which is retained by thedrive lever 11. Accordingly, the drive lever 11 turns in thecounterclockwise direction in FIG. 15A to charge the drive spring 14.

When the drive lever 11 turns in the counterclockwise direction in FIG.15A, the projection portion 11 e of the drive lever 11 is detached fromthe projection portion 15 b of the blade lever 15. Accordingly, theblade lever 15 turns in the counterclockwise direction in FIG. 15B dueto the urging force from the blade return spring 46. In addition, thecam follower 15 e of the blade lever 15 contacts the cam 21 b of thefirst cam gear 21.

Accordingly, the blade lever 15 is kept at the position illustrated inFIG. 15B. In addition, the first blade 41 and the second blade 42maintain the state of closing the aperture 1 a and 2 a.

When the motor (not illustrated) is continuously energized in the drivelever charging state, the second cam gear 22 further rotates. As aresult, the state of the imaging apparatus shifts to a state M (FIG. 6),which illustrates a drive lever charge complete state. The state Millustrated in FIG. 6 corresponds to the drive lever charge completestate.

When the retained roller 13, which is retained by the drive lever 11,reaches the cam top portion 22 d of the second cam 22 c of the secondcam gear 22, the drive lever 11 overcharges the blade drive spring 14.When the energization of the motor is discontinued in this state, thestate of the imaging apparatus shifts to the state A illustrated in FIG.6 (i.e., the pre-release standby state).

FIGS. 16A and 16B illustrate an exemplary shape of the blade cushioningmember 4 and the blade contact member 5. FIG. 16A illustrates the shapeof the blade contact member 5 before assembling the blade contact member5 to the blade cushioning member 4. FIG. 16B illustrates an exemplaryshape of the blade cushioning member 4 before assembling the bladecontact member 5 to the blade cushioning member 4.

Referring to FIG. 16A, the blade contact member 5 always remains incontact with the blade cushioning member 4 by pressing the bladecushioning member 4 with the spring force from arm portions 5 a and 5 balong the side surface of the blade cushioning member 4 when the bladecontact member 5 is assembled to the blade cushioning member 4, tostabilize the state of collision with the blades.

Referring to FIG. 16B, the blade cushioning member 4 includes portions 4a through 4 f. The portion 4 a is provided at a portion of the bladecushioning member 4 lower than the portion 4 d by a predetermined step.The portion 4 b is provided at a portion of the blade cushioning member4 lower than the portion 4 e by a predetermined step.

A hole 4 h is provided to the blade cushioning member 4 at a decenteredportion of the blade cushioning member 4. The shaft portion 1 h of theshutter base plate 1 fits in the hole 4 h. When the blade contact member5 is assembled to the blade cushioning member 4, the portion 4 d of theblade cushioning member 4 is inscribed inside an arm portion 5 a of theblade contact member 5 and the portion 4 e of the blade cushioningmember 4 is inscribed inside an arm portion 5 b of the blade contactmember 5.

When the blade contact member 5 is assembled to the blade cushioningmember 4 in the above-described manner, the portion 4 a is located closeto a bending portion of the arm portion 5 a and the portion 4 b islocated close to a bending portion of the arm portion 5 b. In theexample illustrated in FIG. 16A, the arm portions 5 a and 5 b are bentby an angle of 90° or less. Accordingly, with the effect of the loweredportion 4 a, the arm portion 5 a can easily follow the change of shapeof the blade cushioning member 4 towards the portion 4 d. Similarly,with the effect of the lowered portion 4 b, the arm portion 5 b caneasily follow the change of shape of the blade cushioning member 4towards the portion 4 e.

In addition, With the above-described configuration, even if thefinished dimensions of the portions 4 d and 4 e are set greater than thedimensions of the arm portions 5 a and 5 b, neither the arm portion 5 anor the arm portion 5 b may separate from the portions 4 d and 4 e. Anotch 5 e is formed between portions 5 c and 5 d of the blade contactmember 5. Accordingly, the elastic deformation of the portions 5 c and 5d may not be prevented even if an impact is applied to the portions 5 cand 5 d.

The portion 4 c is a chamfer of the blade cushioning member 4.Accordingly, the blade cushioning member 4 has the shape with which therotation direction and the correct orientation of the blade cushioningmember 4 in relation to the shaft portion 1 h can be verified at aglance.

If the first blade 41 and the second blade 42 collide with the armportion 5 a of the blade contact member 5, the arm portion 5 a iselastically deformed with being pivoted around the bending portion,while the portion 4 d of the blade cushioning member 4 iscompression-deformed. Similarly, if the first blade 41 and the secondblade 42 collide with the arm portion 5 b of the blade contact member 5,each of the arm portion 5 a and the portion 4 d is deformed in theabove-described manner.

On the other hand, if the first blade 41 and the second blade 42 collidewith the portion 5 c of the blade contact member 5, the portion 5 c iselastically deformed with being pivoted around a boundary between theportions 5 c and 5 f, while the portion 4 g of the blade cushioningmember 4 is compression-deformed. Accordingly, the blade contact member5 can be deformed independently from the deformation of the bladecushioning member 4.

FIGS. 17A through 17D illustrate an exemplary method for assembling theblade cushioning member 4 to the shaft portion 1 h.

FIG. 17A is a magnified view of the portions of the blade cushioningmember 4 when the shutter unit 100 is in the unset state illustrated inFIGS. 10A through 10D. FIGS. 17B through 17D illustrate exemplaryorientations of assembling the blade cushioning member 4 to the shaftportion 1 h differently from the example illustrated in FIG. 17A.

Referring to FIGS. 17A through 17D, when the orientation of assemblingthe blade cushioning member 4 by fitting the shaft portion 1 h of theshutter base plate 1 into the hole 4 h of the blade cushioning member 4is changed, the distance between the shaft portion 1 h to the surface ofthe blade cushioning member 4 on which an impact from the first blade 41and the second blade 42 is applied is changed. Dimensions A through Dillustrated in FIGS. 17A through 17D have a relationship of descendingdegree of dimension that can be expressed as B<A<D<C.

Due to any manufacturing dispersion or errors of parts, the distancebetween the shaft portion 1 h and the positions of tips of the firstblade 41 and the second blade 42 may vary at a distance a, b, c, or d asillustrated in FIGS. 17A through 17D. However, a clearance a between theblade cushioning member 4 and the shutter blade can be restricted withina predetermined range by changing the orientation of mounting the bladecushioning member 4 to the shaft portion 1 h. Accordingly, the clearancebetween the first blade 41 and the second blade 42 and the blade contactmember 5 can be adjusted without providing any clearance adjustmentpart.

As described above, in the present exemplary embodiment, the distancefrom the shaft portion 1 h to the surface on which an impact is appliedfrom the first blade 41 and the second blade 42 of the blade cushioningmember 4 can be adjusted at four stages. If the distance from the shaftportion 1 h to the surface on which an impact is applied from the firstblade 41 and the second blade 42 of the blade cushioning member 4 is tobe adjusted at five or six stages, the blade cushioning member 4 and theblade contact member 5 can be given a polygonal shape, such as apentagonal shape or a hexagonal shape.

However, if the blade cushioning member 4 and the blade contact member 5are given the above-described polygonal shape, the dimension of one edgemay become small. As a result, the area of the blade cushioning member 4and the blade contact member 5 large enough to receive an impact fromthe first blade 41 and the second blade 42 without being damaged cannotbe secured. Furthermore, if the size of the blade cushioning member 4and the blade contact member 5 is increased, the sufficiently large areaof the blade cushioning member 4 and the blade contact member 5 may besecured, but this may be neither practical nor useful.

Accordingly, in a modification of the present exemplary embodiment, theblade cushioning member 4 and the blade contact member 5 are combinedtogether in a two-layer configuration. With the above-describedconfiguration, in the modification of the present exemplary embodiment,the distance between the shaft portion 1 h and the above-describedimpact receiving surface can be adjusted at eight stages.

FIGS. 18A through 18C are perspective views illustrating states in whichblade contact members 105A and 105B are assembled to a blade cushioningmember 104. FIG. 18A illustrates an exemplary shape of the bladecushioning member 104 before the blade contact members 105A and 105B areassembled thereto. FIG. 18B is a perspective view illustrating a statein which the blade contact member 105B is assembled to the bladecushioning member 104. FIG. 18C is a perspective view illustrating astate in which the blade contact member 105A is assembled to the bladecushioning member 104.

Referring to FIG. 18A, the shape of the blade cushioning member 104 isformed by two blade cushioning members 4 having different dimensionsmounted together. Referring to FIG. 18B, the blade contact member 105Bis assembled to the blade cushioning member 104 in a small portionthereof. The blade contact member 105B has the same shape as the bladecontact member 5.

Referring to FIG. 18C, the blade contact member 105A is assembled to theblade cushioning member 104 in a large portion thereof. The bladecontact member 105A has the same shape as the blade contact member 5.

FIGS. 19A through 19H illustrate an exemplary method for assembling theblade cushioning member 104 to the shaft portion 1 h. FIG. 19A is amagnified view of the portions of the blade cushioning member 4 when theshutter unit 100 is in the unset state illustrated in FIGS. 10A through10D. FIGS. 19B through 19 h illustrate exemplary orientations ofassembling the blade cushioning member 4 to the shaft portion 1 hdifferently from the example illustrated in FIG. 19A.

Referring to FIGS. 19A through 19H, when the orientation of assemblingthe blade cushioning member 104 by fitting the shaft portion 1 h of theshutter base plate 1 on the blade cushioning member 104 is changed, thedistance between the shaft portion 1 h and the surface of the bladecushioning member 104 on which an impact from the first blade 41 and thesecond blade 42 is applied is changed. A hole into which the shaftportion 1 h of the blade cushioning member 104 is inserted is given tothe blade cushioning member 104 at a decentered position of the bladecushioning member 104.

Due to any manufacturing dispersion or errors of parts, the distancebetween the shaft portion 1 h and the positions of tips of the firstblade 41 and the second blade 42 may vary among distances a through h asillustrated in FIGS. 19A through 19H. However, a clearance a between theblade cushioning member 104 and the shutter blade can be restrictedwithin a predetermined range by changing the orientation of mounting theblade cushioning member 104 to the shaft portion 1 h. Accordingly, theclearance between the first blade 41 and the second blade 42 and theblade contact member 105A or 105B can be adjusted without providing anyclearance adjustment part.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all modifications, equivalent structures, and functions.

This application claims priority from Japanese Patent Application No.2010-261602 filed Nov. 24, 2010, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An imaging apparatus comprising: a mirrorconfigured to advance into or retract from a photographic optical path;a shutter blade configured to close and open an aperture; a blade leverconnected with the shutter blade; a blade return spring configured tourge the blade lever in a direction in which the aperture is opened bythe shutter blade; a drive lever configured to press the blade lever ina direction in which the aperture is closed by the shutter blade; ablade drive spring configured to urge the drive lever in a direction inwhich the aperture is closed by the shutter blade; a first memberconfigured to lock a position of the blade lever to cause the shutterblade to shift to a state of closing the aperture; and a second memberconfigured to cause the mirror to advance into the photographic opticalpath at a first position and to cause the mirror to retract from thephotographic optical path at a second position, wherein, the secondmember is driven from the first position to the second position afterthe first member has unlocked the blade lever so that the shutter bladeis driven in the direction of opening the aperture by an urging force ofthe blade return spring before the mirror starts an operation forretracting from the photographic optical path.
 2. The imaging apparatusaccording to claim 1, wherein the first member further comprises a firstgear portion and the second member further comprises a second gearportion, which is configured to engage the first gear portion, andwherein the first gear portion and the second gear portion areconfigured to engage each other to drive the second member from thefirst position to the second position after the first member hasunlocked the blade lever.
 3. The imaging apparatus according to claim 1,wherein the second member is configured to charge the blade drive springby moving the drive lever, and wherein the second member is configuredto charge the blade drive spring after the second member is driven fromthe second position to the first position.
 4. The imaging apparatusaccording to claim 1, further comprising a mirror lever configured tocause the mirror to advance into the photographic optical path when thesecond member is positioned at the first position and to cause themirror to retract from the photographic optical path when the secondmember is positioned at the second position, wherein the second memberfurther comprises a first cam portion configured to engage the mirrorlever, and a second cam portion configured to engage the drive lever. 5.The imaging apparatus according to claim 1, wherein the shutter blade ismade of a polyethylene terephthalate (PET) material containing ablackening.